1exportfs(8) System Manager's Manual exportfs(8)
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6 exportfs - maintain list of NFS exported file systems
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9 /usr/sbin/exportfs [-avi] [-o options,..] [client:/path ..]
10 /usr/sbin/exportfs -r [-v]
11 /usr/sbin/exportfs [-av] -u [client:/path ..]
12 /usr/sbin/exportfs [-v]
13 /usr/sbin/exportfs -f
14
16 The exportfs command is used to maintain the current table of exported
17 file systems for NFS. This list is kept in a separate file named
18 /var/lib/nfs/etab which is read by mountd when a remote host requests
19 access to mount a file tree, and parts of the list which are active are
20 kept in the kernel's export table.
21 Normally this etab file is initialized with the list of all file sys‐
23 tems named in /etc/exports by invoking exportfs -a.
24 However, administrators can choose to add and delete individual file
26 systems without modifying /etc/exports using exportfs.
27 exportfs and it's partner program mountd work in one of two modes, a
29 legacy mode which applies to 2.4 and earlier versions of the Linux ker‐
30 nel, and a new mode which applies to 2.6 and later versions providing
31 the nfsd virtual filesystem has been mounted at /proc/fs/nfsd or
32 /proc/fs/nfs. If this filesystem is not mounted in 2.6, the legacy
33 mode is used.
34 In the new mode, exportfs does not give any information to the kernel
36 but only provides it to mountd through the /var/lib/nfs/etab file.
37 mountd will listen to requests from the kernel and will provide infor‐
38 mation as needed.
39 In the legacy mode, any export requests which identify a specific host
41 (rather than a subnet or netgroup etc) are entered directly into the
42 kernel's export table as well as being written to /var/lib/nfs/etab.
43 Further, any mount points listed in /var/lib/nfs/rmtab which match a
44 non host-specific export request will cause an appropriate export entry
45 for the host given in rmtab to be entered into the kernel's export ta‐
46 ble.
47
49 -a Export or unexport all directories.
50 -o options,...
52 Specify a list of export options in the same manner as in
53 exports(5).
54 -i Ignore the /etc/exports file, so that only default options and
56 options given on the command line are used.
57 -r Reexport all directories. It synchronizes /var/lib/nfs/etab with
59 /etc/exports. It removes entries in /var/lib/nfs/etab which are
60 deleted from /etc/exports, and remove any entries from the ker‐
61 nel export table which are no longer valid.
62 -u Unexport one or more directories.
64 -f In 'new' mode, flush everything out of the kernels export table.
66 Any clients that are active will get new entries added by mountd
67 when they make their next request.
68 -v Be verbose. When exporting or unexporting, show what's going on.
70 When displaying the current export list, also display the list
71 of export options.
72
74 Exporting Directories
75 The first synopsis shows how to invoke the command when adding new
76 entries to the export table. When using exportfs -a, all directories
77 in exports(5) are added to etab and the resulting list is pushed into
78 the kernel.
79 The host:/path argument specifies the directory to export along with
81 the host or hosts to export it to. All formats described in exports(5)
82 are supported; to export a directory to the world, simply specify
83 :/path.
84 The export options for a particular host/directory pair derive from
86 several sources. There is a set of default options which can be over‐
87 ridden by entries in /etc/exports (unless the -i option is given). In
88 addition, the administrator may override any options from these sources
89 using the -o argument which takes a comma-separated list of options in
90 the same fashion as one would specify them in exports(5). Thus,
91 exportfs can also be used to modify the export options of an already
92 exported directory.
93 Modifications of the kernel export table used by nfsd(8) take place
95 immediately after parsing the command line and updating the etab file.
96 The default export options are sync,ro,root_squash,wdelay.
98 Unexporting Directories
100 The third synopsis shows how to unexported a currently exported direc‐
101 tory. When using exportfs -ua, all entries listed in etab are removed
102 from the kernel export tables, and the file is cleared. This effec‐
103 tively shuts down all NFS activity.
104 To remove individual export entries, one can specify a host:/path pair.
106 This deletes the specified entry from etab and removes the correspond‐
107 ing kernel entry (if any).
108 Dumping the Export Table
110 Invoking exportfs without further options shows the current list of
111 exported file systems. When giving the -v option, the list of flags
112 pertaining to each export are shown in addition.
113
115 The following adds all directories listed in /etc/exports to
116 /var/lib/nfs/etab and pushes the resulting export entries into the ker‐
117 nel:
118 # exportfs -a
120 To export the /usr/tmp directory to host djando, allowing asynchronous
122 writes, one would do this:
123 # exportfs -o async django:/usr/tmp
125
127 Exporting to IP networks, DNS and NIS domains does not enable clients
128 from these groups to access NFS immediately; rather, these sorts of
129 exports are hints to mountd(8) to grant any mount requests from these
130 clients. This is usually not a big problem, because any existing
131 mounts are preserved in rmtab across reboots.
132 When unexporting a network or domain entry, any current exports to mem‐
134 bers of this group will be checked against the remaining valid exports
135 and if they themselves are no longer valid they will be removed.
136
138 exports(5), mountd(8)
139
141 Olaf Kirch, <okir@monad.swb.de>
142 Neil Brown, <neilb@cse.unsw.edu.au>
143 18 July 2003 exportfs(8)